Methods and systems for the hierarchical mesh restoration of connections in an automatically switched optical network

ABSTRACT

The present disclosure describes methods and systems for the hierarchical mesh restoration of connections in an ASON or the like. These methods and systems provide a mesh restorable OTN server layer that carries an aggregate of mesh restorable SONET/SDH SNCs, without designating SONET/SDH/OTN hand-off ports or work/protect lines. Server layer SNCs are terminated on Virtual Trail Termination Points (VTTPs) on the NEs. These VTTPs maintain all of the attributes of physical Trail Termination Points (TTPs). The server routing protocol creates physical TTP interfaces at the server layer, and the server layer advertises bandwidth to the client layer routing protocol. A failure in the server layer results in the mesh restoration of an aggregate line, holding off the release of the individual client SNCs. Only when the server layer cannot restore are these individual client SNCs released.

FIELD OF THE INVENTION

The present invention relates generally to the optical networking field.More specifically, the present invention relates to methods and systemsfor the hierarchical mesh restoration of connections in an AutomaticallySwitched Optical Network (ASON) or the like.

BACKGROUND OF THE INVENTION

An ASON is a network that enables the automatic delivery of transportservices, including leased-line connections and other transportservices, such as switched and soft-permanent optical connections. TheASON provides a framework for protection switching and reutilization isarticulated by Generalized Multi-Protocol Label Switching (GMPLS) or thelike. In an ASON, each network node is equipped with a control planethat sets up and releases connections, and may restore a connection inthe case of a failure. These control planes may be thought of asswitches. ITU-T Recommendation G.8080, “Architecture for theautomatically switched optical network (ASON),” describes the set ofcontrol plane components that are used to manipulate the transportnetwork resources, including the setting up, maintaining, and releasingof connections. A switched connection is set up and released from aNetwork Management System (NMS) that uses network generated signalingand routing protocols to establish the connection. Connections in anASON are typically Synchronous Optical Network/Synchronous DigitalHierarchy (SONET/SDH) or Optical Transport Network (OTN). Thearchitectures for these connections are described in ITU-TRecommendations G.803 and G.872, respectively.

Referring to FIG. 1, in an ASON 10, a connection may originally berequested from either a client device 12 a, 12 b (in which case theconnection is referred to as a Switched Connection (SC) 14) or a NMSinterface 16 (in which case the connection is referred to as aSoft-Permanent Connection (SPC) 18). In this exemplary embodiment, theASON 10 includes three control domains: Domain A 20, Domain B 22, andDomain C 24, and six Network Elements (NEs) 30,32,34,36,38,40. Therequesting entity may be part of any control domain 20,22,24 or part ofan external network.

Domain A 20 includes NEs 30,32 as Border Nodes (BNs), Domain B 22includes NEs 34,36 as BNs, and Domain C 24 includes NEs 38,40 as BNs.Each of these control domains 20,22,24 may include additional NEsbetween the BNs (not illustrated), and these are referred to asIntermediate Nodes (INs). In this exemplary embodiment, the clients 12a, 12 b connect to the NEs 30,40, respectively, via an OpticalUser-to-Network Interface (O-UNI). This enables control planeinteroperability between the clients 12 a, 12 b and the control domains20,22,24. The control domains 20,22,24 interconnect via ExternalNetwork-to-Network Interfaces (E-NNIs)—between NEs 32 and 34 for theinterconnection of Domain A 20 and Domain B 22, and between NEs 36 and38 for the interconnection of Domain B 22 and Domain C 24.

Sub-Network Connections (SNCs) 42,44,46 originate from one BN of anetwork (i.e. control domains 20,22,24) and terminate on another BN ofthe same network (i.e. control domains 20,22,24). In FIG. 1, SNC 42originates from NE 30 and terminates on NE 32, SNC 44 originates from NE34 and terminates on NE 36, and SNC 46 originates from NE 38 andterminates on NE 40. The links between NEs 32 and 34, and 36 and 38 areE-NNI links. The end NEs 30,40 across the control domains 20,22,24 maybe SC clients that originate and terminate the SC 14. Typically, the SC14 or SPC 18 includes multiple SNCs 42,44,46. The connections 14,18 mayalso include SONET/SDH services or Ethernet resources.

With the increase in demand for data traffic, ASONs are rapidly growingin size and total bandwidth, reaching hundreds of nodes. This increasein size and total bandwidth results in a large volume of messages beinghandled by the control planes. Processing power must increase and/or theefficiency of routing algorithms must improve if network restorationperformance is to be maintained. Being finite, processing power and theefficiency of routing algorithms represent a real limitation on thescalability of a mesh network. This scalability problem may easily beimagined for lines that carry multiple SNCs in a large network. Thefailure of such a line requires the re-routing of all SNCs.

To solve this problem, mesh restoration may be combined withconventional line based protection at the server or line layer. Serverlayer protection is typically applied on the SONET/SDH line, or OpticalTransport Unit/Optical Data Unit (OTUk/ODUk) path if the opticaltransport layer is used. Combining mesh restoration with conventionallines based protection increases performance and scalability, butrequires significant network planning and introduces topologylimitations. All of these line based methods require predeterminedprotection bandwidth and are topology dependent (i.e. ring based orpoint-to-point).

Combining SONET/SDH and OTN mesh networks is possible given the currentstate-of-the-art, but requires a clear demarcation and fixed hand-offbetween the two. This is even more undesirable than the former case, asthese fixed hand-offs require additional protection.

Thus, what is needed in the art are methods and systems that provide amesh restorable OTN server layer that carries an aggregate of meshrestorable SONET/SDH SNCs, without designating SONET/SDH/OTN hand-offports or work/protect lines.

BRIEF SUMMARY OF THE INVENTION

In various exemplary embodiments, the present invention provides methodsand systems for the hierarchical mesh restoration of connections in anASON or the like. These methods and systems provide a mesh restorableOTN server layer that carries an aggregate of mesh restorable SONET/SDHSNCs, without designating SONET/SDH/OTN hand-off ports or work/protectlines. Server layer SNCs are terminated on Virtual Trail TerminationPoints (VTTPs) on the NEs. These VTTPs maintain all of the attributes ofphysical Trail Termination Points (TTPs). The server routing protocolcreates physical TTP interfaces at the server layer, and the serverlayer advertises bandwidth to the client layer routing protocol. Afailure in the server layer results in the mesh restoration of anaggregate line, holding off the release of the individual client SNCs.Only when the server layer cannot restore are these individual clientSNCs released.

In an exemplary embodiment, a method for hierarchical mesh restorationsof connections in an Automatically Switched Optical Network includesreceiving a request to create a Virtual Sub Network Connection, whereinthe Virtual Sub Network Connection includes a defined payload type;creating an originating Virtual Connection Point at an originating node;creating a terminating Virtual Connection Point at a terminating node;and mapping the defined payload type to the originating VirtualConnection Point and the terminating Virtual Connection Point. Themethod can further include creating an Optical Data Unit TrailTermination Point through an Optical Transport Network signal androuting protocol. Optionally, the method further includes auto-creatinga SONET/SDH Trail Termination responsive to creating the Optical DataUnit Trail Termination Point; creating a SONET/SDH ConnectionTermination Point through a SONET/SDH signal and routing protocol; andcreating cross connects in a switch matrix. Alternatively, the methodfurther includes advertising available bandwidth in terms of OpticalTransport Network bandwidth. The method can include responsive to afailure, mesh restoring the Virtual Sub Network Connection; and ifunable to mesh restore the Virtual Sub Network Connection, performingone of standard mesh restoration and Local Span Mesh Restoration.Optionally, the method is performed by an optical switch including oneor more line modules; a switch matrix interconnecting each of the one ormore line modules, wherein the switch matrix is configured to switch ateach of Optical Transport Network, SONET, and SDH layers; wherein theswitch matrix is configured to operate responsive to an OpticalTransport Network signal and routing protocol and a SONET/SDH signal androuting protocol.

In another exemplary embodiment, an optical switch includes one or moreline modules, wherein the one or more line modules are configured toterminate each of Optical Transport Network, SONET, and SDH; a switchmatrix interconnecting each of the one or more line modules; wherein theswitch matrix is configured to operate responsive to an OpticalTransport Network signal and routing protocol and a SONET/SDH signal androuting protocol; wherein the Optical Transport Network signal androuting protocol is configured to provide restoration of Optical DataUnit and Optical Channel Payload Virtual Container Sub NetworkConnections. The one or more line modules are configured to terminateeach of Optical Transport Network, SONET, and SDH; and the switch matrixis configured to switch at each of Optical Transport Network, SONET, andSDH layers. The optical switch can further include one or more OpticalData Unit Sub Network Connections each terminated on a Virtual TrailTermination Point. Optionally, the optical switch further includes anOptical Transport Unit Trail Termination Point terminating a physicalOptical Transport Network signal to an Optical Channel Data Unit signal;an Optical Data Unit Trail Termination Point terminating the OpticalChannel Data Unit signal to a Synchronous Transport Module signal; and aSynchronous Transport Module Trail Termination Point terminating theOptical Channel Data Unit signal to a plurality of Administrative Unitsconnected to a plurality of Connection Termination Points in the switchmatrix. The optical switch can also include a Virtual Trail TerminationPoint configured to logically terminate Synchronous Transport Module andOptical Channel Data Unit trails. The Optical Transport Network signaland routing protocol is configured to create the Optical Data Unit TrailTermination Point and the Synchronous Transport Module Trail TerminationPoint; and the SONET/SDH signal and routing protocol is configured tocreate the Synchronous Transport Module Trail Termination Point andcross connects in the switch matrix. The restoration can include meshrestoring a plurality of Optical Transport Network Sub NetworkConnections between Virtual Connection Points on physical interfaces onthe one or more line modules; and if unable to restore the plurality ofOptical Transport Network Sub Network Connections, performing one ofstandard mesh restoration and Local Span Mesh Restoration.

In yet another exemplary embodiment, an Automatically Switch OpticalNetwork includes a plurality of interconnected nodes; an OpticalTransport Network signal and routing protocol communicating to each ofthe plurality of nodes; a SONET/SDH signal and routing protocolcommunicating to each of the plurality of nodes; wherein the OpticalTransport Network signal and routing protocol is configured to providerestoration of Optical Data Unit and Optical Channel Payload VirtualContainer Sub Network Connections. The Optical Transport Network signaland routing protocol communicates to each of the plurality of nodesthrough a General Communication Channel; and the SONET/SDH signal androuting protocol communicates to each of the plurality of nodes througha Data Communication Channel. The General Communication Channeladvertises Optical Transport Network bandwidth and the DataCommunication Channel advertises SONET/SDH bandwidth. The restorationcan include mesh restoring a plurality of Optical Transport Network SubNetwork Connections between Virtual Connection Points on physicalinterfaces; and if unable to restore the plurality of Optical TransportNetwork Sub Network Connections, performing one of standard meshrestoration and Local Span Mesh Restoration.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated and described herein with referenceto the various drawings, in which like reference numbers are used todenote like method steps/system components, as appropriate, and inwhich:

FIG. 1 is a schematic diagram illustrating a conventional ASON;

FIG. 2 is a schematic diagram illustrating a conventional method forusing an OTN SNC to realize a SNC highway;

FIG. 3 is another schematic diagram (network layer model) illustrating aconventional method for using an OTN SNC to realize a SNC highway;

FIG. 4 is a schematic diagram illustrating one exemplary embodiment of amethod for exploiting an OTN SNC using a VTTP in accordance with thepresent invention;

FIG. 5 is another schematic diagram (network layer model) illustratingone exemplary embodiment of a method for exploiting an OTN SNC using aVTTP in accordance with the present invention;

FIG. 6 is a schematic diagram of a provisioning view of VTP SNC (VSNC)termination in an optical switch in accordance with the presentinvention;

FIG. 7 is schematic diagram of various objects created in a switchmatrix in accordance with the present invention;

FIG. 8 is a schematic diagram illustrating example connections that aresupported by the VTTP methods and systems of the present invention; and

FIG. 9 is another schematic diagram illustrating example connections andhow they are handled in the absence of the VTTP methods and systems ofthe present invention;

FIG. 10 is a diagram of an OTN OSRP line, such as an OTU2 Link, definedat the OTUk network layer;

FIG. 11 is a network diagram of a network of optical cross connects(OCXs) illustrating an example of embedded SONET/SDH links with OTNlinks; and

FIGS. 12—19 are diagrams illustrating various exemplary embodiments ofOTN OSRP object creation and deletion.

DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is to create an OTN layer thatprovides for the mesh restoration of ODUx and Optical Channel PayloadVirtual Container (OPVCx) SNCs. The OTN layer is modeled based on theconventional SONET/SDH model. OC-192—SONET TTP is analogous to OTU2—OTNTTP and STS-1/Nc—SONET Connection Termination Point (CTP) is analogousto ODUx/OPVCx—OTN CTP. Advantageously, the Line Modules (LMs) used arecapable of terminating both the OTN and SONET/SDH layers and switchingat either layer. As a result, a single physical OTN interface may haveboth an OTN TTP and one or more SONET/SDH TTPs within it.

The network is operated as distinct layers. OTN bandwidth is advertisedvia the General Communication Channel (GCC) and SONET/SDH bandwidth isadvertised via the Data Communication Channel (DCC), or alternativelyover an out-of-band communication channel for OSRP (e.g., through an IPnetwork). OTN bandwidth is advertised in terms of the available ODU2,ODU1, and OPVC bandwidth. An OTU2 with no connections advertises supportfor 1xODU2, 4xODU1, 16-64xOPVC (ORP Lite), for example. A common portgroup mode must be supported for these applications. Thus, a FieldProgrammable Gate Array (FPGA) load that supports an ODU2 cross connectmust also support NxODU1 and NxOPVC. A given OTN interface may supportboth SONET/SDH and OTN connections, but the SONET/SDH portion of thebandwidth must be allocated by the user—the control plane itself doesnot determine this. An OTN SNC that carries SONET/SDH is OTN bandwidth.There is no need to define the SONET/SDH bandwidth on intermediatenodes—only at the origination/termination points.

Referring to FIG. 2, an OTN SNC may be used to realize a SNC highway. ASONET line (OC-48/192) is mapped into an ODUx, and then an ODUx SNC iscreated. A signaling and routing protocol, such as Optical Signaling andRouting Protocol (OSRP), at the SONET level sees Chicago and New York asdirect neighbors. Any size connection may utilize the bandwidth and theSNCs are provisioned on an end-to-end basis. An outage on the linkresults in an ODUx SNC mesh restoration. If an ODUx is unable torestore, the SONET line within it is failed and standard meshrestoration or Local Span Mesh Restoration (LSMR) is applied. In effect,the bundle is allowed to splinter and restore on any availablebandwidth. A single OTU2 may be broken up into 4xODU1 and support4xOC-48, or a single ODU2 and support an OC-192. FIG. 2 illustratesthese SONET SNCs 50, ODUx CTPs 52, and this ODUx SNC 54.

Referring to FIG. 3, the network layer model 60 includes multipleoptical switches (SONET) 62,64, multiple optical switches (SONET/OTN)66,68, and multiple optical switches (OTN) 70,72. Line Modules (LMs)67,69 used at the SONET/OTN switches 66,68 are capable of terminatingboth the SONET and OTN layers and switching at either layer. The crossconnects of the SONET switches 62,64 and SONET/OTN switches 66,68 arecoupled via SONET lines 74,76, and the cross connects of the SONET/OTNswitches 66,68 and OTN switches 70,72 are coupled via OTU lines78,80,82. The various TTPs and CTPs are illustrated, including OC48 TTPs84,86, ODU1 TTPs 88,90, and OTU2/ODU2 TTPs 92,94. The SONET SNC 96 spansthe SONET-SONET/OTN-OTN-SONET/OTN-SONET realm, while the OTN SNC 98spans the OTN realm.

Referring to FIG. 4, in one exemplary embodiment of the presentinvention, an OTN SNC uses a VTTP. Advantageously, a physical hand-offis not required to start the OTN SNC, and the OTN SNC originates on aNE, not on a port. The VTTP is a compound object: (SONET clientVTTP+server ODUx VTTP+ODUx VCP). The OTN SNC is then created between theODUx VCPs at the origination and terminating nodes. Since the ODUx VCPis created in the fabric, an OTN SNC that originates on it may meshrestore to any physical interface. The SONET VTTP is remapped to a newphysical interface as the OTN SNC is created or mesh restored. FIG. 4illustrates these SONET SNCs 50, this ODUx SNC 54, these SONET CTPs 100,SONET VCPs 102, SONET VTTPs 104, and ODUx VTP with SONET VTPs 106. Note,the ODU_CTP and VCP do not need to be exposed to the management system.

Referring to FIG. 5, the network layer model 110 again includes multipleoptical switches (SONET) 62,64, multiple optical switches (SONET/OTN)66,68, and multiple optical switches (OTN) 70,72. The LMs 67,69 used atthe SONET/OTN switches 66,68 are capable of terminating both the SONETand OTN layers, i.e. capable of terminating SONET lines, OTUk section,and ODUk/OPVCx paths, and switching at either layer. The cross connectsof the SONET switches 62,64 and SONET/OTN switches 66,68 are coupled viaSONET lines 74,76, and the cross connects of the SONET/OTN switches66,68 and OTN switches 70,72 are coupled via OTU lines 78,80,82. Thevarious TTPs and CTPs are illustrated, including OC48 TTPs 84,86, ODU1TTPs 88,90, and OTU2/ODU2 TTPs 92,94. The VCP/VTPs 112,114 describedabove are also illustrated. The SONET SNC 96 spans theSONET-SONET/OTN-OTN-SONET/OTN-SONET realm, while The OTN SNC 118 spansthe SONET/OTN-OTN-SONET/OTN realm.

Referring to FIG. 6, a provisioning view 200 of VTP SNC (VSNC)termination in an optical switch is illustrated according to anexemplary embodiment of the present invention. The optical switchincludes network ports 202 (e.g., OC-48/STM-16, OC-192/STM-64, OTU2,OTU3, etc.), a switch matrix 204, and a switch backplane 206 (e.g.,electrical, optical, etc.). The switch backplane 206 is configured tophysically connect each of the network ports 202 and the switch matrix204, and the switch matrix 204 is configured to provide cross connectionbetween various connections of the network ports 202 including thesetting up, maintaining, and releasing of connections. The provisioningview 200 is illustrated with regard to OTU1s, and those of ordinaryskill in the art will recognize that OTU2, OTU3, etc. are alsocontemplated by the present invention.

The optical switch is configured to receive OTU1 210 traffic from one ormore or the network ports 202, i.e. up to four OTU1s per 10 G portgroup. Each OTU1 210 has associated overhead data including, forexample, OTU1 overhead fault information, performance monitoring data,GCC, and the like. A network administrator/operator 212 can define anODU-1 VTP SNC endpoint 214 with, for example, a payload type(SONET/SDH), OTU1 overhead fault information, performance monitoringdata, GCC, and the like. Accordingly, a compound VTTP is created whichincludes all three components (ODU VCP+ODUVTTP+SONETVTTP). Those threethings are connected in “lock-step” together, but strictly speaking, theODU-1 SNC would terminate on the ODU-1VCP. In the present invention, theODU-1VCP is always attached to the child VTTP, so it is not necessary toexpose the ODU VCP in the management interface.

Responsive to defining the ODU-1 VTP SNC endpoint 214, a switch androuting protocol, such as OSRP, can create an ODU1 TTP 216 with adefined payload type, OTU1 overhead fault information, performancemonitoring data, GCC, and the like. Next, a SONET/SDH TTP 218 isauto-created responsive to the ODU1 TTP 216 with a defined payload type(e.g., OC-48/STM-16, etc.), a supporting Termination Point (TP), atimeslot map, overhead information, DCC information, and the like.

A SONET/SDH signaling and routing protocol 220, such as OSRP, creates aSONET/SDH CTP 222 with a defined type, timeslot map, size, supportingcross-connect information, supporting TP information, associated GTP,overhead information, and the like. Also, the signaling and routingprotocol 220 creates the SONET/SDH CTP in the switch matrix 204.

Accordingly, the OSRP can auto-create OTN TTPs within the switch matrix204 since it has to size larger interfaces to smaller sizes on the fly.This effort overcomes the slow user interfaces that are used today. Thisworks to create the correct LM setup as well in addition to the switchmatrix 204. Once created, the new OTN TTPs 216 work as normal TTPs dotoday with connectable timeslots. Also, the switch matrix 204 is stillfast since this is still a matter of moving pointers around. Theprovisioning view 200 illustrates an exemplary operation of creating OTNTTPs in accordance with the present invention.

The STMn/ODU VTTP represents the logical STMn/ODU line. The STMn TPmaintains all the STMn line attributes, including capacity (timeslotusage), operational state, etc. The resources (timeslots in this case)are advertised at the SONET/SDH layer ORP, a pointer is provided to thephysical STMn/ODU TTP currently supporting the VCx_CTP→VCx_VCPcross-connect. The STMn timeslot resources are freely advertised to theSONET/SDH layer and participate in SONET/SDH OSRP just like any otherregular line.

If the physical OTUk line goes down, the ODU SNC is released back to theVTTP, deleting the ODU_CTP→ODU_VCP cross-connect. The OTN OSRP routingprotocol will then attempt to find another operational OTUk line tobuild a new physical STMn/ODU TTP and re-establish a new ODU_CTP→ODU_VCPcross-connect. Once the new physical TTP is constructed, VCP pointersare updated and the VCx_CTP→VCx_VCP cross-connect is maintained for thetransiting SONET/SDH SNCs.

The line state for the STMn logical line is still up during the OTNre-route, so SONET SNCs using it will not release or perform LSMR unlessthe OTN layer was unable to restore, in which case the STMn logical linestate would go down. A timer may be implemented here.

Referring to FIG. 7, a functional view 300 illustrates various objectscreated in a switch matrix 302 in accordance with the present invention.The functional view 300 utilizes topology components described in ITU-TRecommendation G.805, “Generic functional architecture of transportnetworks.” The functional view 300 illustrates physical connections(Point-to-Point, PTP) 304,306 with the connection 304 including an OTNconnection and the connection 306 including a Synchronous TransportModule (STM) (SDH) connection.

The OTN connection 304 is physically terminated first on a OTUk TTP 308from an OTUk to an ODUk. Next, the connection 304 is physicallyterminated on an ODUk TTP 310 from an ODUk to a Constant Bit Rate (CBR)signal. The CBR signal is an STM which is terminated on an STMn TTP 312to an Administrative Unit (AU). The STM connection 306 is physicallyterminated on an STMn TTP 314 to an AU. Various VCx SNCs 320 arecross-connected through CTPs 322, 324, but are terminated elsewhere inthe SONET/SDH network.

As described herein, the present invention includes a VTTP 330 toprovide termination of logical SDH and ODUk trails. The VTTP 330provides a termination of an ODUk SNC 332 and an STMn NC (networkconnection) 334. For example, the ODUk SNC 332 can terminate on an ODU2VTTO with a CBR payload type. The ODUk SNC 332 and the STMn NC 334 areaccordingly terminated at Virtual Connection Points (VCPs) 336. Note,the ODUk SNC 332 and the STMn NC 334 are always routed together.

In the present invention, an OTN signal and routing protocol, such asOSRP, is configured to create the ODUk TTP 310 and the STMn TTPs 312,314on the line side of a terminating node. The parameters for these TTPs310,312,314 are maintained by the VTTP 330. A SONET/SDH signal androuting protocol is configured to create CTPs 322,324 and cross-connectswith the switch matrix 302.

Referring to FIG. 8, a single ODU SNC 400 may be created to supportconnections from all adjacent nodes 402,404. The connections from theseadjacent nodes are not bound to the highway, and the SNCs may switch toany available output on the nodes 406,408.

The present invention enables switching at the line level not theindividual connection. This provides a new construct of a “VTTPHighway”. This represents a virtual TTP connection that goes between twonodes (but could transverse many nodes to get there), e.g. nodes406,408. From a signal and routing protocol's connection perspective, itappears that it is a normal TTP that goes to another “adjacent” node.The key is that it is not bound to a physical line. It is a logicalrepresentation like traditional line protection. Therefore the physicalline can be changed without the application (connection OSRP, forexample) knowing or having to react at the connection level. Theswitching of the “VTTP Highway” is really switching of the ODUk pathusing OSRP, and the SONET line comes along for the ride. So theadjacency is with respect to SONET across the OTN network.

With regard to failures, the VTTP version of the signal and routingprotocol determine an alternate “OTN highway” of matched OTN sizebetween the origination and destination nodes, e.g. nodes 406,408. If itcannot find one, it marks the VTTP “down” which starts theconnection-based switch and routing protocol doing normal connectionswitching. If it can find an alternate route, it uses signaling tocreate OTN TTPs on these nodes within a switch core (and the LMs) as inOTN SNCs.

On the originating and terminating nodes for the VTTP highway, e.g.nodes 406,408, a “line based” switch occurs with the VTTP being switchedfrom/to the new OTN TTPs. This is similar to Automatic ProtectionSwitching (APS). The switch and routing protocol does not have to worryabout the connections on the VTTP. It sees the entire VTTP as aconnection. It simply tells the switch core to create the new OTN TTPand then switch the VTTP TLPI to the new OTN TTP TLPI. A VTTP switch androuting protocol leverages the OTN SNC routing and bandwidth managementto be able to determine alternate VTTPs. For example, Designated TransitLists (DTL's) can be available for VTTP highways since they handled likeconnections.

Referring to FIG. 9, without the VTTP, an ODU SNC 410 per interface mustbe created. The first SNC is unchanged. The next two SNCs must beswitched to a node that supports a given highway. A SNC that does notwant to ride the highway must be switched on other bandwidth.

For example, conventional mechanisms utilize a greedy algorithm forconnection-based switching. Physical lines include timeslots that aregrouped together. Each timeslot has a head timeslot (for concatenation)and a pointer to a potential cross-connect (in case it is in acrossconnect). At boot up, all timeslots are associated with theirphysical lines.

TTPs are user created and have physical timeslots moved to them. So ifthere is an OTU2 physical line, and an ODU2 is created, all 192timeslots are owned by the TTP. This allows applications tocross-connect to them. Also if an ODU1 is created on timeslot 1 on theODU2, the first 48 timeslots are moved to the new ODU1 TTP. TTPs areindexed by TxnLogicalPortIds (TLPIs) which are 32 bit numbers thatindicate what type of line, in what LM slot, at which TBU startingtimeslot,

For line based protection switching, when an application like VirtualLine Switched Ring (VLSR) or APS wants to switch from a work line to aprotect line, it tells the switch core to copy the timeslot pointersfrom one TTP (via its TLPI) to another and select from the new source.At this point switch core is sending to both lines but listening totraffic from the protect. This is a relatively fast operation since nonew memory is created.

The signal and routing protocol, such as OSRP, can establish a suitablecross-connect to support a given SNC. For example, the followingcross-connects are supported: ODU2, ODU1, and OPVC1-Xn (X=1-16). Asystem can support OTN SNC network side interfaces on LMs configured tosupport both SONET/SDH and OTN on PTPs with provisioned servicetype-OTUk (k=1, 2).

The OTN signal and routing protocol, e.g. an OTN OSRP, can utilize theGCC bytes in the G.709 overheard. For example, because some DWDMequipment terminates GCC0, the OTN OSRP can use GCC(1, 2) for OSRProuting and signaling. When using such equipment for DWDM transport, theGCC channel must remain active in order for the OTUk OSRP line to remainup. This includes cases where ODUk maintenance signals are present. Itis therefore necessary to alter treatment of PM overhead bytes for OSRPlines using GCC(1, 2). When a communication protocol (including OSRP) isenabled on an OTUk interface using GCC1, or GCC2, or GCC(1+2), thesystem can read and terminate the GCC1 and/or GCC2 bytes. Thisrequirement includes cases where the ODUk layer is cross-connected.

When communication protocol (including OSRP) is enabled on an OTUkinterface using GCC1, or GCC2, or GCC(1+2), the system can generate newGCC1 and/or GCC2 bytes in the PM overhead. This requirement includescases where the ODUk layer is cross-connected. When communicationprotocol (including OSRP) is enabled on GCC1, or GCC2, or GCC(1+2), thesystem can read and write messages in the GCC bytes, even in thepresence of a maintenance signal. Maintenance signals include: ODU-AIS,ODU-OCI, and OCU-LCK. When communication protocol (including OSRP) isenabled on GCC1, or GCC2, or GCC(1+2), the system can read and writemessages in the GCC bytes while inserting a maintenance signal towardthe line. Maintenance signals include: ODU-AIS, ODU-OCI, and OCU-LCK.[R]

Referring to FIG. 10, with respect to OTN OSRP routing, an OTN OSRPline, such as an OTU2 Link 500, is defined at the OTUk network layer.Embedded OTN TTPs, such as OTU2 TTPs 502,504, are not considered OSRPlines, although provisioning of embedded lines restricts the availablebandwidth, and determines the size and type of bandwidth advertised. TheOTN OSRP link 500 is defined as one or more OSRP lines. Routing on OTUkOSRP lines can be enabled or disabled. OTUk lines can advertisebandwidth (BW) on the given line according to the following rules:

Provisioned interface scenario: Advertised BW OTU2 only ODU2 4 × ODU1 16× OPVC1 OTU2 with ODU2 TTP, PT = 20 with available (1-4) × ODU1 ODU1timeslots 16 × OPVC1 OTU1 only ODU1 16 × OPVC1 OTU2 with one or moreODU1 TTP, at least one (1-3) × ODU1 empty ODU1 timeslot, one ODU1 TTP PT= (1-16) × OPVC1 0x80 with available timeslots OTU2 with 4 × ODU1 TTP,one ODU1 TTP PT = 1-16 OPVC1 0x80 with available timeslots

In order to prevent inefficient use of bandwidth, the system can providea mechanism to limit the minimum connection size on the link asdescribed in the following table:

Line Min. Connection Size - interface allowed values OTU1 ODU1, OPVC1Default = OPVC1 OTU2 ODU2, ODU1, OPVC1 Default = OPVC1The system does not allow SNCs smaller than the minimum connection sizeto use a given link. For example, a bandwidth update is sent when thenumber of available ODU1 timeslots on a link changes. When the actualavailable bandwidth changes to ODU2, a new routing update can begenerated. When the maximum available bandwidth on a link changes toNxOPVC (N=1-16), the available bandwidth advertised in any outgoingrouting update is NxOPVC. Only OTUk lines can be capable of having OTNOSRP routing enabled. Embedded ODUk do not participate in routing andsignaling for OTN OSRP. Note that embedded SONET/SDH lines are capableof supporting routing for SONET/SDH OSRP.

If child TTPs are embedded SONET/SDH, the system treats them as separatelines (in routing/signaling and ISCC) and routing could be enabled onthose lines. Embedded SONET/SDH lines can have routing enabled ordisabled. Node adjacency for OTN and SONET/SDH is specific to thetraffic type. Adjacency for an OTN link is determined by OTUk TTPs,whereas SONET/SDH adjacency is determined by SONET Line or SDH MS TTPs.The system can provide a provisioning interface to enable routing overGCCn on the OTUk interface.

FIG. 10 illustrates an example of TTP in Open Connection Indication(OCI). In a first configuration, the system advertises the OSRP line asdown for lines that have one or more manually created TTPs (i.e., ODU2TTP 506 with a plurality of ODU1 timeslots 508) in OCI alarm. Thisapplies to cases where a termination point is provisioned at one end ofthe link, but not the other. In a second configuration, the systemsadvertises 4xODU1 bandwidth on the OTU2 link when both sides includeODU2 TTPs 506,510 with the plurality of ODU1 timeslots 508.

Referring to FIG. 11, a network 550 of optical cross connects (OCXs) 552a, 552 b, 552 c, 552 d illustrates an example of embedded SONET/SDHlinks 554 with OTN links 556 in accordance with the present invention.Each OXC 552 generally includes a switch matrix (SM) 570 connected toone or more line modules (LMs) 572. The connection can include anelectrical, optical, etc. backplane, midplane, etc. The switch matrix570 is configured to provide switching at an optical layer (wavelength)and/or electrical layer (SONET/SDH/OTN). The switch matrix 570 providesswitching of connections between each of the one or more line modules572. The line modules 572 can be configured to receive SONET/SDH, OTN,or the like. The line modules 572 can also be configured to performprocessing and switching of SONET/SDH, OTN, or the like. In general, theOXCs 552 are configured to implement the present invention describedherein. For example, the switch matrix 570 can include representation ofthe various OTN SNCs. The OXCs 552 can include management interfacesthrough external interfaces or SONET/SDH or OTN overhead.

A Designated Transit List (DTL) can support a DTL Traffic Typeparameter, restricting links to either SONET/SDH or OTN. This allowschecking at DTL and DTLSet to not allow mix and match of DTLs as well asduring SNC provisioning. SONET/SDH DTLs allow the use of embeddedSONET/SDH lines over ODUk/OTUk. Note that intermediate transparent nodessupporting OTN cross-connects do not terminate the SONET/SDH line, andare not considered part of a SONET/SDH DTL.

FIG. 11 illustrates an exemplary case where the SONET/SDH link (S1) 554is embedded in the OTUk/ODUk lines 556. Adjacency for the OCx/STMn link554 is between OXCs 552 a⇄552 d. Accordingly, OXC B is transparent forSONET/SDH link S1 554. Maintaining bundle diversity is not a requirementfor SONET/SDH SNCs, where a SONET/SDH mesh network is carried over anOTN mesh network. The OXCx 552 can support all various DTL types andassociated behavior for OTN SNCs include Working DTL, HierarchicalProtect DTL, Associated Hop Protect, Manual Switch to Protect,Pre-Computed Protect, Current Route DTL, and Home Route DTL.

Failure of an OTUk OSRP line 556 causes all SNCs on the supporting lineto release and attempt restoration. The following OTUk faults shall failthe OTN OSRP line and initiate release messaging: OTUk-LOF (Loss ofFrame), OTUk-AIS (Alarm Indication Signal), OTUk-LOS (Loss of Signal),OTUk-TIM (Trail Trace Identifier Mismatch), and OTUk-BDI (BackwardDefect Indication). The system can support SNC Integrity Check (SNCIC)for OTN SNCs. Behavior of SNCIC is consistent with SONET/SDH SNCICbehavior.

The network 500 and the associated OXCs 552 can initiate meshrestoration for OTN SNCs upon SNCIC failure. The following defectsdetected at the origination and termination points (e.g., each OXC 552with OTUk links 556) can fail SNCIC for ODUk SNCs: ODUk-AIS, ODUk-BDI,ODUk-OCI, and ODUk-LCK (Locked). Note that ODUk-LCK and ODUk-OCI pathdefects are not typically be present at SNC endpoints. It is possiblethat intermediate equipment could generate these defects. The followingdefects detected at the origination and termination points shall failSNCIC for OPVC1-Xn SNCs: OPVC-AIS, OPVC-BDI, OPVC-OCI, and OPVC-LCK.Note that OPVC-LCK and OPVC-OCI path defects would not typically bepresent at SNC endpoints. It is possible that intermediate equipmentcould generate these defects.

When an OTN facility object is in dependency due to equipment failure,the OXC 552 can send a release for all SNCs on the facility object andinitiate mesh restoration. A TM failure or reboot during cross-connectcreation shall initiate a release for the supported OTN SNC. OTN SNCscan support Max Admin Weight as described in the OSRP. The Admin weightcan be expanded to include separate cost and latency attributes. TheOXCs 552 can support termination of OTN SNCs on a CTP or GTP supportingtransparent interfaces; i.e. a CTP or GTP that belongs to an OCGsupporting a CBR_TTP.

Referring to FIGS. 12 through 19, OTN OSRP object creation and deletionis illustrated in accordance with the present invention. OTN OSRP can becapable of creating the following types of cross-connects for thecorresponding SNC: ODU2Xcon, ODU1Xcon, and OPVCXcon. Once an availableline is selected, the system can create the line side facility objectsto support the SNC. In the simplest case, a CTP and cross-connect iscreated on a pre-provisioned TTP. More complex cases require creation ofTTP supporting objects. Drop side TTP objects are always manuallycreated.

The OXC can support both manually created and auto-created TTPs and/orCTPs on the same ODUk TTP interface. The OXC can also support bothmanually created PVC cross-connects and auto created OSRP cross-connectson the same OTUk. In order to support an ODU2 SNC, the OXC can becapable of auto creating an ODU2 CTP on an idle, enabled OTU2 TTP, asillustrated in an ODU2 SNC line side interface 600 in FIG. 12.

The OXC can be capable of auto creating the following line sideinterfaces to support ODU1 SNCs: ODU1 CTP created on an OTU1 TTP that isidle, but operationally enabled, as illustrated in an ODU1 SNC line sideinterface on an OTU1 602 in FIG. 13; ODU1 CTP created on an ODU2 TTPthat is not busy (i.e., has open timeslots) and is operationallyenabled, as illustrated in an ODU1 SNC line side interface on an ODU2 inFIG. 14; ODU1 CTP and ODU2 TTP created on an OTU2 TTP that is idle, butoperationally enabled, as illustrated in an ODU1 SNC line side interfaceon an OTU2 in FIG. 15.

The OXC shall be capable of auto creating the following line sideinterfaces to support OPVC1-Xn SNCs: OPVC CTP and ODU1 TTP created on anOTU1 TTP that is idle, but operationally enabled, as illustrated by anOPVC SNC line side interface on an OTU1 608 in FIG. 16; OPVC CTP createdon an ODU1/ODU2 TTP that is not busy (i.e., has open timeslots) and isoperationally enabled, as illustrated by OPVC SNC line side interfaceson ODU1/ODU2 610,612 in FIG. 17; OPVC CTP and ODU1 TTP created on anODU2 TTP that is not busy (i.e., has open timeslots) and isoperationally enabled, as illustrated on an OPVC SNC line side interfaceon an ODU2 614 in FIG. 18; and OPVC CTP, ODU1 TTP, and ODU TTP createdon an ODU2 TTP that is idle, but operationally enabled, as illustratedon an OPVC SNC line side interface 616 in FIG. 19.

ODUk TTPs that are auto-created by OSRP are created with the appropriatepayload type code in order to support the child TTP or CTP objects.Payload type codes for auto-created TTPs are read-only. With theexception of payload type, ODUk TTPs that are auto-created by OSRP arecreated with the MO default values. In order to meet mesh restorationperformance requirements the system prioritizes establishment of thedata-path. This may occur prior to presenting the TP object attributesto the management interface. The system allows creation of manuallyprovisioned cross-connects on TTPs created by OSRP. The system canauto-delete TTPs created by OSRP after the TTP has been idle for 1second. An idle TTP is defined as a TTP that does not support any higherlayer termination or connection.

Although the present invention has been illustrated and described hereinwith reference to preferred embodiments and specific examples thereof,it will be readily apparent to those of ordinary skill in the art thatother embodiments and examples may perform similar functions and/orachieve like results. All such equivalent embodiments and examples arewithin the spirit and scope of the present invention, are contemplatedthereby, and are intended to be covered by the following claims.

What is claimed is:
 1. A method for hierarchical mesh restorations ofconnections in an Automatically Switched Optical Network, comprising:receiving a request to create a Virtual Sub Network Connection, whereinthe Virtual Sub Network Connection comprises a defined payload type,wherein the Virtual Sub Network Connection comprises an OpticalTransport Network (OTN) Sub Network Connection carrying a combination ofOTN, Synchronous Optical Network (SONET), and Synchronous DigitalHierarchy (SDH) signals such that OTN, SONET, and SDH signals eachparticipate in a same mesh restoration scheme at an OTN, SONET, and SDHlayer, and wherein SONET and SDH bandwidth is only defined atorigination and termination points of the Virtual Sub Network Connectionwhereas OTN bandwidth is defined at each point of the Virtual SubNetwork Connection; creating an originating Virtual Connection Point atan originating node; creating a terminating Virtual Connection Point ata terminating node; mapping the defined payload type to the originatingVirtual Connection Point and the terminating Virtual Connection Point;responsive to a failure, performing mesh restoration in a hierarchicalmanner, wherein the hierarchical manner comprises: a) attempting to meshrestore the Virtual Sub Network Connection; and b) if unable to meshrestore the Virtual Sub Network Connection, splintering the Virtual SubNetwork Connection into individual connections and restoring theindividual connections by performing one of standard mesh restorationand Local Span Mesh Restoration of individual Sub Network Connectionswithin the Virtual Sub Network Connection.
 2. The method of claim 1,further comprising: creating an Optical Data Unit Trail TerminationPoint through an Optical Transport Network signal and routing protocol.3. The method of claim 2, further comprising: auto-creating a SONET/SDHTrail Termination responsive to creating the Optical Data Unit TrailTermination Point.
 4. The method of claim 3, further comprising:creating a SONET/SDH Connection Termination Point through a SONET/SDHsignal and routing protocol; and creating cross connects in a switchmatrix.
 5. The method of claim 2, further comprising: advertisingavailable bandwidth in terms of Optical Transport Network bandwidth. 6.The method of claim 1, wherein the method is performed by an opticalswitch comprising: one or more line modules; and a switch matrixinterconnecting each of the one or more line modules, wherein the switchmatrix is configured to switch at each of Optical Transport Network,SONET, SDH layers; wherein the switch matrix is configured to operateresponsive to an Optical Transport Network signal and routing protocoland a SONET/SDH signal and routing protocol.
 7. An optical switch,comprising: one or more line modules, wherein the one or more linemodules are configured to terminate each of Optical Transport Network,SONET, or SDH; a switch matrix interconnecting each of the one or moreline modules; wherein the switch matrix is configured to operateresponsive to an Optical Transport Network signal and routing protocolor a SONET/SDH signal and routing protocol; wherein the OpticalTransport Network signal and routing protocol is configured to providerestoration of Optical Data Unit and Optical Channel Payload VirtualContainer Sub Network Connections; wherein, responsive to a failure,mesh restoration is performed in a hierarchical manner comprising: a)attempting to mesh restore the Optical Data Unit and Optical ChannelPayload Virtual Container Sub Network Connections; and b) if unable tomesh restore the Optical Data Unit and Optical Channel Payload VirtualContainer Sub Network Connections, splintering the individual SubNetwork Connections within the Optical Data Unit and Optical ChannelPayload Virtual Container Sub Network Connections into individualconnections and restoring the individual connections through one ofstandard mesh restoration-and Local Span Mesh restoration; wherein theOptical Data Unit and Optical Channel Payload Virtual Container SubNetwork Connections comprise an Optical Transport Network (OTN) SubNetwork Connection carrying a combination of OTN, Synchronous OpticalNetwork (SONET), and Synchronous Digital Hierarchy (SDH) signals suchthat OTN, SONET, and SDH signals each participate in a same meshrestoration scheme at an OTN, SONET, and SDH layer, and wherein SONETand SDH bandwidth is only defined at origination and termination pointsof the Virtual Sub Network Connection whereas OTN bandwidth is definedat each point of the Virtual Sub Network Connection.
 8. The opticalswitch of claim 7, wherein the one or more line modules are configuredto terminate each of Optical Transport Network, SONET, and SDH; andwherein the switch matrix is configured to switch at each of OpticalTransport Network, SONET, and SDH layers.
 9. The optical switch of claim7, further comprising: one or more Optical Data Unit Sub NetworkConnections each terminated on a Virtual Trail Termination Point. 10.The optical switch of claim 7, further comprising: an Optical TransportUnit Trail Termination Point terminating a physical Optical TransportNetwork signal to an Optical Channel Data Unit signal; an Optical DataUnit Trail Termination Point terminating the Optical Channel Data Unitsignal to a Synchronous Transport Module signal; and a SynchronousTransport Module Trail Termination Point terminating the Optical ChannelData Unit signal to a plurality of Administrative Units connected to aplurality of Connection Termination Points in the switch matrix.
 11. Theoptical switch of claim 10, further comprising: a Virtual TrailTermination Point configured to logically terminate SynchronousTransport Module and Optical Channel Data Unit trails.
 12. The opticalswitch of claim 11, wherein the Optical Transport Network signal androuting protocol is configured to create the Optical Data Unit TrailTermination Point and the Synchronous Transport Module Trail TerminationPoint; and wherein the SONET/SDH signal and routing protocol isconfigured to create the Synchronous Transport Module Trail TerminationPoint and cross connects in the switch matrix.
 13. The optical switch ofclaim 7, wherein the restoration comprises: mesh restoring a pluralityof Optical Transport Network Sub Network Connections between VirtualConnection Points on physical interfaces on the one or more linemodules; and if unable to restore the plurality of Optical TransportNetwork Sub Network Connections, performing one of standard meshrestoration and Local Span Mesh Restoration.
 14. An AutomaticallySwitched Optical Network, comprising: a plurality of interconnectednodes; an Optical Transport Network signal and routing protocolcommunicating to each of the plurality of nodes; and a SONET/SDH signaland routing protocol communicating to each of the plurality of nodes;wherein the Optical Transport Network signal and routing protocol isconfigured to provide restoration of Optical Data Unit and OpticalChannel Payload Virtual Container Sub Network Connections; wherein,responsive to a failure, mesh restoration is performed in a hierarchicalmanner comprising: a) attempting to mesh restore the Optical Data Unitand Optical Channel Payload Virtual Container Sub Network Connections;and b) if unable to mesh restore the Optical Data Unit and OpticalChannel Payload Virtual Container Sub Network Connections, splinteringthe individual Sub Network Connections within the Optical Data Unit andOptical Channel Payload Virtual Container Sub Network Connections intoindividual connections and restoring the individual connections throughone of standard mesh restoration-and Local Span Mesh restoration;wherein the Optical Data Unit and Optical Channel Payload VirtualContainer Sub Network Connections comprise an Optical Transport Network(OTN) Sub Network Connection carrying a combination of OTN, SynchronousOptical Network (SONET), and Synchronous Digital Hierarchy (SDH) signalssuch that OTN, SONET, and SDH signals each participate in a same meshrestoration scheme at an OTN, SONET, and SDH laver, and wherein SONETand SDH bandwidth is only defined at origination and termination pointsof the Virtual Sub Network Connection whereas OTN bandwidth is definedat each point of the Virtual Sub Network Connection.
 15. TheAutomatically Switched Optical Network of claim 14, wherein the OpticalTransport Network signal and routing protocol communicates to each ofthe plurality of nodes through a General Communication Channel; andwherein the SONET/SDH signal and routing protocol communicates to eachof the plurality of nodes through a Data Communication Channel.
 16. TheAutomatically Switched Optical Network of claim 15, wherein the GeneralCommunication Channel advertises Optical Transport Network bandwidth andthe Data Communication Channel advertises SONET/SDH bandwidth.
 17. TheAutomatically Switched Optical Network of claim 14, wherein therestoration comprises: mesh restoring a plurality of Optical TransportNetwork Sub Network Connections between Virtual Connection Points onphysical interfaces; and if unable to restore the plurality of OpticalTransport Network Sub Network Connections, performing one of standardmesh restoration and Local Span Mesh Restoration.